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Development of the in-situ cosmogenic 14C method for studying geomorphic processes

开发用于研究地貌过程的原位宇宙成因 14C 方法

基本信息

批准号：
9304193
负责人：
Devendra Lal
金额：
$ 10.77万
依托单位：
University of California-San Diego Scripps Inst of Oceanography
依托单位国家：
美国
项目类别：
Continuing Grant
财政年份：
1993
资助国家：
美国
起止时间：
1993-07-01 至 1996-06-30
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=9304193&HistoricalAwards=false
关键词：
Development situ cosmogenic 14C method

项目摘要

This research will complete the development of an experimental method for measuring in situ cosmogenic 14C (half-life=5730 yrs) in common surficial terrestrial materials, and for making pilot studies of the method for investigating a few challenging geomorphic problems. From the work carried out to date under NSF grant, we have in hand an experimental method, potentially capable of providing accurate and contamination-free (from environmental 14C) measurements of 14C concentrations. Instead of the commonly adopted method of high temperature fusion, we developed a wet in vacuo method to determine the in situ 14C concentrations in the CO and CO2 phases in the mineral quartz. Environmental 14C does not affect the 14CO measurements, but appears erratically as contamination in the 14CO2 measurement. Since more than 60% of in situ 14C appears in the CO phase, it is convenient to assay in situ 14C by measuring its activity in the CO phase. During the first year, work will primarily be directed towards the development of a robust experimental technique to accurately measure in situ 14C concentration at levels of x104 atoms 14C/g quartz, and the determination of in situ 14C production rates in quartz at different altitudes and latitudes. The latter is a prerequisite for its applications. In the second year, we propose to make some test applications of the in situ 14C method to a number of selected geomorphic problems. It may appear that little can be done in such challenging problems in just one year but we are able to do this because we have at a suite of diverse geomorphic samples in which in situ cosmogenic 10Be and 26Al studies have made earlier in our group. We believe that among the various in situ radionuclides, 14C should offer the most convenient approach for characterizing geomorphic surfaces, providing a firm basis for decisions for further analyses using other in situ radionuclides, e.g. 36Cl, 26Al and 10Be, and the stable nuclide, 21Ne. We are very anxious to complete the development of the experimental method to reliably measure in situ cosmogenic 14C in surficial samples, and to demonstrate its usefulness in geomorphology. //

这项研究将完成一个实验性的发展，在大气中原位测量宇宙成因14 C（半衰期=5730年）的方法常见的地表材料，并用于制作飞行员研究了几种具有挑战性的研究方法，地貌问题根据NSF迄今为止开展的工作，格兰特，我们有一个实验性的方法，有可能提供准确和无污染（从环境 14 C）测量14 C浓度。而不是通常的采用高温熔融的方法，研制了一种湿法烧结的真空法原位测定CO中~（14）C浓度和CO2相。环境14 C不影响14 CO测量，但似乎不稳定， 14 CO2测量中的污染。由于超过60%的原位~（14）C出现在CO相中，便于原位测定 14 C通过测量其在CO相中的活性。在第一今年，工作将主要针对发展一个用于精确测量原位14 C的可靠实验技术浓度在x104原子14 C/g石英的水平，不同温度下石英中原位~（14）C产生率的测定高度和纬度。后者是其前提。应用. 在第二年，我们建议进行一些测试应用原位14 C方法对一些选定的地貌问题在这种情况下，似乎无能为力。在短短一年的时间里，我们就能解决这些具有挑战性的问题，因为我们有一套不同的地貌样本，在宇宙成因的10 Be和26 Al原位研究中，组我们认为，在各种原位放射性核素中，14 C 应该提供最方便的方法来表征地貌表面，为决策提供坚实的基础，使用其他原位放射性核素（如36 Cl、26 Al）的进一步分析 10 Be和稳定核素21 Ne。我们非常渴望完成实验方法的开发，在地表样品中原位测量宇宙成因的14 C，证明了它在地貌学上的用处。 //